浮点数比较

由于计算机中浮点数并不是精确表示，所以两个浮点数不能直接比较，而是要在一个误差范围内比较。

有的文章还要用相对误差比较。我用到地方都只需要绝对误差比较就行了。绝对误差 eps=1e-8

#define  eps 1e-8
#pragma inline=forced
 int double_cmp_biger( double data1,double data2 )
{
 return (int)( (data1-data2)> eps);
}
#pragma inline=forced
 int double_cmp_smaller( double data1,double data2 )
{
 return (int)( (data2-data1)> eps);
}

#pragma inline=forced
int double_cmp_equar_biger( double data1,double data2 )
{
    // return (int) ((double_cmp_biger(data1,data2)) || ( !double_cmp_smaller(data1,data2)))  ;
 return (int) ( !double_cmp_smaller(data1,data2))  ;
}
#pragma inline=forced
 int double_cmp_equar_smaller( double data1,double data2 )
{
    // return (int) ((!double_cmp_biger(data1,data2)) || ( double_cmp_smaller(data1,data2)))  ;
     return (int) (!double_cmp_biger(data1,data2))  ;
}

#pragma inline=forced
 int double_cmp_equar_no( double data1,double data2 )
{
    return (int) (double_cmp_biger(data1,data2 ) || double_cmp_smaller(data1,data2 )  )  ;
}

#pragma inline=forced
int double_cmp_equar( double data1,double data2 )
{
    return !double_cmp_equar_no(  data1, data2 );
}

#pragma inline=forced
int cmp_double(double a,double b) // 小 -1 等 0 大 1
{
    a-=b;
    return a < -eps ? -1 : a < eps ? 0 : 1;
    
}